The present invention relates to detectors of the type used in vending machines to detect that a product released from a magazine in the machine has fallen into a dispensing chute and, in particular, to a device for optically detecting that an object has fallen.
A single vending machine can offer to the public a wide variety of products with each product marketed in a different sized package. A customer seeking to use the machine will deposit sufficient sums of money into the machine to pay for the product chosen and then use a keyboard or the like to select the desired product. After determining that the funds deposited are adequate to pay for the chosen product, an electronic controller in the machine signals a dispensing device for the magazine retaining the selected product. When the machine operates properly, the dispensing device removes one of the selected products from the magazine and allows it to drop into a chute which tapers down to a dispensing tray were it can be removed by the customer.
It has been found, however, that for any of a number of reasons, such machines sometimes fail to dispense a product. A product will not be dispensed if the selected magazine is empty or if the service personnel who last refilled the machine failed to insert products in all of the pigeon-holes of the selected magazine and the dispensing device attempted to dispense a product from an empty pigeon-hole. Even if there is product in the selected magazine, the dispensing device may be defective or jammed and be unable to carry out a dispensing cycle. A product dispensed from its dispensing device may also become stuck or hung up within the machine such that it is never available to the customer.
If a purchased product has not been dispensed to a customer, the customer is entitled to the return of the funds he has deposited in the machine. Existing vending machines have detectors for detecting whether a product has fallen through the chute to the tray for removal by the customer, and before refunding the customer""s money, the electronic controller running the machine is programmed to attempt corrective measures. The electronic controller will first send a second a signal to the dispensing device for the selected magazine to dispense a second product. Where the dispensing device failed to dispense a product because of an empty pigeon-hole in a magazine, or because the dispensed product became jammed or hung up in the machine, a second dispensing may result in a product being properly dispensed.
If a product has not been detected as having dropped through the chute after the second attempt, the electronic controller might call for the dispensing of yet a third product. In fact, the electronic controllers of many existing vending machines are programmed to continue calling for the dispensing of product until a product has detected as having dropped through the chute or until a predetermined number of attempts have been made, after which the machine will refund the money deposited by the customer. The proper operation of such vending machines therefor require that a signal be sent to the electronic controller each time a product has been properly dispensed.
One method of accurately recording the dispensing of a product is to provide a detector, such as a microswitch, for monitoring the removal of every product in the machine. The network of detectors required to monitor all the products in the machine, however, would greatly complicate the manufacture of the machine and the electronics required would greatly increase its cost. Existing machines currently use ultrasonic devices or radio waves for detecting the movement of a product through the chute to the tray, however such detectors have not been entirely satisfactory. The equipment required to generate and receive electro magnet signals, essentially a radar, is expensive to manufacture and maintain. On the other hand, ultra sonic devices which detect the sound made as a product hits the tray at the bottom of the chute are easily compromised by a customer who reaches his hand into the tray to catch the falling product before it thumps against the walls of the chute or the tray. By catching the product, the acoustical detector fails to detect that a product has been dropped and the electronic controller signals for the dropping of a second product, which the customer might also catch. A customer with a degree of dexterity could catch a half a dozen falling products after paying for only one.
It would be desirable to provide an optical system which would use inexpensive LED emitters and detectors to detect a falling product because such a device could be easily integrated into the circuitry of the machine. Prior efforts to make a light curtain consisting of a plurality of LED emitters along one side of a dispensing chute and a plurality of LED detectors along the opposite side have not been successful because infrared light emitters do project a narrow beam of light. The light from one emitter is inevitably received by several or all of the detectors on the opposite side of the chute making it difficult for the micro-processor to discern when a object has fallen through the curtain. There is, therefore, a need to provide an optical detector for detecting the movement of a product through a chute which will overcome the problems encountered with respect to the use of infrared emitters and receivers.
Briefly, the present invention is an improvement to a vending machine of the type having a magazine for retaining a plurality of dispensable products. The machine has a dispensing means for dispensing one product in a magazine at a time. The machine further has a discharge chute through which dispensed products are dropped to an outlet tray. The discharge chute has a cross sectional area defined by a first side and a second opposing side, and the machine further includes a means for detecting that one of a plurality of dispensable products has passed through the cross sectional area.
In accordance with the invention, the means for detecting that a product has passed through the cross sectional area includes a plurality of optical emitters spaced along the first side of the chute with the emitters aimed towards the second side where a second plurality of spaced receptors are positioned to receive the signals from the emitters. The spacing between adjacent receptors is small enough that an optical signal from one of the plurality of optical emitters will be received by more than one of the receptors.
The invention further includes a sequencing circuit for sequentially illuminating each one of the optical emitters and a means for determining that one of the receptors has failed to receive a beam directed towards it from on of the emitters.
An important feature of the invention is that the sequencing circuit must complete a cycle of illuminating all the emitters forming the light curtain during the brief interval of time that a product is passing through the cross sectional area of the light curtain. The permitted interval of time can be determined by calculating the speed of the product after it has fallen out of the magazine to the light curtain and the vertical height of the product as it passes through the plane of the light curtain.